Phylogeny of a serotonin-immunoreactive neuron in the primary olfactory center of the insect brain

Andrew M. Dacks, Thomas A. Christensen, John G Hildebrand

Research output: Contribution to journalArticle

80 Citations (Scopus)

Abstract

Serotonin (5-hydroxytryptamine; 5HT) functions in insects as a neurotransmitter, neuromodulator, and neurohormone. In the sphinx moth Manduca sexta, each of the paired antennal lobes (ALs; the primary olfactory centers in the insect brain) has one 5HT-immunoreactive (5HT-ir) neuron that projects into the protocerebrum, crosses the posterior midline, and innervates the contralateral AL; this is referred to as the contralaterally projecting, serotonin-immunoreactive deutocerebral (CSD) neuron. These neurons are thought to function as centrifugal modulators of olfactory sensitivity. To examine the phylogenetic distribution of 5HT-ir neurons apparently homologous to the CSD neuron, we imaged 5HT-like immunoreactivity in the brains of 40 species of insects belonging to 38 families in nine orders. CSD neurons were found in other Lepidoptera, Trichoptera, Diptera, Coleoptera, and Neuroptera but not in the Hymenoptera. In the paraneopteran and polyneopteran species (insects that undergo incomplete metamorphosis) examined, AL 5HT neurons innervate the ispsilateral AL and project to the protocerebrum. Our findings suggest that the characteristic morphology of the CSD neurons originated in the holometabolous insects (those that undergo complete metamorphosis) and were lost in the Hymenoptera. In a subset of the Diptera, the CSD neurons branch within the contralateral AL and project back to the ipsilateral AL via the antennal commissure. The evolution of AL 5HT neurons is discussed in the context of the physiological actions of 5HT observed in the lepidopteran AL.

Original languageEnglish (US)
Pages (from-to)727-746
Number of pages20
JournalJournal of Comparative Neurology
Volume498
Issue number6
DOIs
StatePublished - Oct 20 2006

Fingerprint

Phylogeny
Insects
Serotonin
Neurons
Brain
Neurotransmitter Agents
Hymenoptera
Diptera
Manduca
Lepidoptera
Moths
Beetles

Keywords

  • Antennal lobe
  • Immunocytochemistry
  • Insect
  • Phylogeny
  • Serotonin

ASJC Scopus subject areas

  • Neuroscience(all)

Cite this

Phylogeny of a serotonin-immunoreactive neuron in the primary olfactory center of the insect brain. / Dacks, Andrew M.; Christensen, Thomas A.; Hildebrand, John G.

In: Journal of Comparative Neurology, Vol. 498, No. 6, 20.10.2006, p. 727-746.

Research output: Contribution to journalArticle

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